Insecticide resistance in Australian Spodoptera frugiperda (J.E. Smith) and development of testing procedures for resistance surveillance

Abstract

Spodoptera frugiperda (J.E. Smith) is a highly invasive noctuid pest first reported in northern Australia during early 2020. To document current status of resistance in S. frugiperda in Australia, insecticide toxicity was tested in field populations collected during the first year of establishment, between March 2020 and March 2021. Dose-response was measured by larval bioassay in 11 populations of S. frugiperda and a susceptible laboratory strain of Helicoverpa armigera. Emamectin benzoate was the most efficacious insecticide (LC50 0.023μg/ml) followed by chlorantraniliprole (LC50 0.055μg/ml), spinetoram (LC50 0.098μg/ml), spinosad (LC50 0.526μg/ml), and methoxyfenozide (1.413μg/ml). Indoxacarb was the least toxic selective insecticide on S. frugiperda (LC50 3.789μg/ml). Emamectin benzoate, chlorantraniliprole and methoxyfenozide were 2- to 7-fold less toxic on S. frugiperda compared with H. armigera while spinosyns were equally toxic on both species. Indoxacarb was 28-fold less toxic on S. frugiperda compared with H. armigera. There was decreased sensitivity to Group 1 insecticides and synthetic pyrethroids in S. frugiperda compared with H. armigera: toxicity was reduced up to 11-fold for methomyl, 56 to 199-fold for cyhalothrin, and 44 to 132-fold for alpha cypermethrin. Synergism bioassays with metabolic inhibitors suggest involvement of mixed function oxidase in pyrethroid resistance. Recommended diagnostic doses for emamectin benzoate, chlorantraniliprole, spinetoram, spinosad, methoxyfenozide and indoxacarb are 0.19, 1.0, 0.75, 6, 12 and 48μg/μl, respectively.

Resistance bioassays and allele characterisation inform analysis ofSpodoptera frugiperda(Lepidoptera: Noctuidae) introduction pathways in Asia and Australia

“…frugiperda in the invasive range is increasingly being recognised as may not be as rapid and widespread as originally believed (e.g., Naghoshi et al 2022;Rane et al 2022;Jiang et al 2022). As such, we advocate cautionary approaches to avoid premature assumptions that extensive population admixture via gene flow in Australia landscape would lead to homogenised populations and therefore the approach to combine multiple distantly sampled populations in bioassay studies (e.g., Bird et al 2022).…”

“…Bioassays testing of a larger population pooled from several sites or several individual populations from multiple sites would be especially relevant in a pest capable of high dispersal across the landscape, however the spread of S. frugiperda in the invasive range is increasingly being recognised as may not be as rapid and widespread as originally believed (e.g., Naghoshi et al 2022; Rane et al 2022; Tay et al 2022a; Jiang et al 2022). As such, we advocate cautionary approaches to avoid premature assumptions that extensive population admixture via gene flow in Australia landscape would lead to homogenised populations and therefore the approach to combine multiple distantly sampled populations in bioassay studies (e.g., Bird et al 2022).…”

“…Initially the GR colony was periodically replenished to sustain population genetic diversity and minimise inbreeding but no new material has been introduced for around two decades and the colony is susceptible to many chemical insecticides, including organochlorines, organophosphates, carbamates and pyrethroids, as well as to the Cry1Ab, Cry1Ac, and Cry2Ab Bt toxins (Pearce et al 2017a, Pearce et al 2017b). It therefore has tolerance levels that are not dissimilar to those of a progenitor population created in 2011 that was deliberately maintained as susceptible through screening (see Bird et al 2021). The H. armigera GR population was confirmed by bioassays as having no Cry1Ac/Cry2Ab/VIP3A resistance alleles.…”

“…To provide a first insight into the efficacy of key compounds and toxins we compared the responses of S. frugiperda with two related major endemic crop pests in Australia, Helicoverpa armigera (subspecies conferta; Hardwick 1965, Anderson et al 2016, Pearce et al 2017b, a, Zhang et al 2022) and S. litura , which are currently managed through adaptive resistance management plans. Finally, we provided a critical review of resistance profiles in selected invasive populations of S. frugiperda globally to better understand its invasion biology, and consider our work alongside a subsequent more comprehensive examination in Australia of insecticide resistance profiles (Bird et al 2022). Our study is the only available information for Australian populations on the vulnerability of new arrived S. frugiperda to relevant Bt toxins.…”

Metal–Organic Framework (UiO-66)-Based Temperature-Responsive Pesticide Delivery System for Controlled Release and Enhanced Insecticidal Performance against Spodoptera frugiperda

“…frugiperda control. , According to a previous report, the IC 50 of IDC to S. frugiperda (Australia) is only 3.789 μg/mL, indicating the high efficiency of IDC . However, IDC is an insoluble pesticide, and most used formulations are suspension concentrate and emulsifiable concentrate, which are of poor stability, burst release, and high toxicity. , Therefore, the exploration of environmentally friendly and high-efficiency IDC formulation is necessary.…”